The suitability of Anastrepha spp. and Ceratitis capitata larvae as hosts of Diachasmimorpha longicaudata and Diachasmimorpha tryoni : Effects of host age and radiation dose and implications for quality control in mass rearing

Abstract

The emergence of parasitoids from irradiated tephritid host larvae of different species and ages was evaluated. Parasitoid and fly longevity and fecundity resulting from each treatment were also assessed. Doses of 5, 10, 20, 30, 40, 50, 80, 100 and 150 Gy were applied to samples (100 larvae) of 6-, 7-, 8- and 9-day-old Anastrepha spp. larvae (A. ludens (Loew), A. obliqua (Mcquart) and A. serpentina (Wiedemann)) and 6- and 7-day-old Ceratitis capitata (Wiedemann) larvae. Anastrepha larvae were exposed to Diachasmimorpha longicaudata (Ashmead), and C. capitata larvae to D. tryoni (Cameron). Following larval exposures of 20 Gy, fly emergence was totally suppressed in all larval ages of A. ludens and A. serpentina, while in A. obliqua and C. capitata, total suppression was achieved at 30 Gy. In all species, fly emergence decreased with increasing radiation dosages from 5 to 20 Gy. Emerged fly fertility and longevity also decreased as the radiation increased. On the other hand, parasitoids did not suffer decreases in longevity or fecundity as host radiation dose increased. Larval age at the time of irradiation did not influence emergence, longevity and fecundity of either flies or parasitoids. When the irradiated cohort size was raised to one liter of larvae (about 32,000 Anastrepha or 50,000 C. capitata larvae) a dose of 40 Gy in A. ludens, A. serpentina and A. obliqua totally suppressed fly emergence but permitted D. longicaudata emergence, while for C. capitata larvae, it was necessary to increase the dose to 60 Gy. Quality control tests under mass rearing conditions were applied to D. longicaudata reared using irradiated A. ludens larvae. There was no statistical difference between parasitoids derived from irradiated or non-irradiated host for most parameters. Only percent pupation after 72 h differed, along with the consequent differences between the percent emergence and pupal weight. The conclusions drawn from this study lead to a greater flexibility in the use of irradiated hosts in the mass rearing of the fruit fly parasitoids D. longicaudata and D. tryoni.